Vertical cavity surface emitting lasers (hereinafter referred to as “VCSELs”) have become the dominant light source for optical transmitters used in short-reach local area networks and storage area network applications, in which a multi-mode optical fiber is used for data transmission. VCSELs are low cost micro-cavity devices with high speed, low drive current and low power dissipation, with desirable beam properties that significantly simplify their optical packaging and testing. In order to extend the application of VCSELs to higher speed applications, the VCSEL must be capable of operating reliably at frequencies of up to 10 GHz.
Commercial oxide confined VCSELs have been widely deployed in the field. However, due to intrinsic mechanical stress introduced by the oxidation in the VCSEL fabrication, oxide confined VCSELs are not as reliable as, for example, proton (or ion) implanted VCSELs with higher random failure rates. Prior art VCSELs which include an oxide confinement may operate at 10 GHz, but they suffer from poor reliability. Prior art ion implanted VCSELs typically operate at about 1 GHz, but-are more reliable than VCSELs with oxide confinement. Although certain stress relief methods may be introduced to reduce the random failure rate, the oxidation process is too sensitive to the temperature, materials composition, and gas pressure during device fabrication and, therefore, the oxide confinement process is not a consistent manufacturing process for VCSELs.
Ion implanted VCSELs are relatively more reliable. However, ion implanted devices do not perform well at higher speeds and, therefore, their applications are limited to data rates around 1 Gbps. The speed of an ion implanted VCSEL is limited by several factors. One factor is the lack of a good index guiding for the optical mode. Another factor is from a size limitation due to a deep implant where the typical implant depth may be more than three microns. Further, the implant has a distribution with a large straggle and a large standard deviation. With a large implant distribution and the poor current confinement of a heavily doped mirror, the size is typically more than 20 microns wherein the speed is limited to less than 2 GHz.
Therefore, there is a need to develop a reliable high performance VCSEL for high speed optical communications.
Accordingly, it is an object of the present invention to provide new and improved VCSELs that operate reliably at high frequencies.
It is another object of the present invention to provide new and improved VCSELs with reduced current leakage and device capacitance.